Compositions and methods for the treatment and prevention of disease in plants

ABSTRACT

Non-toxic, naturally derived and economical compositions for treating and preventing bacterial or fungal disease in plants, especially citrus canker, wherein such compositions include various combinations of d-limonene, wax and monohydric alcohol are provided. Methods for making and using such compositions are also provided.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for thetreatment and prevention of bacterial and fungal disease in plants.Among the important diseases which can be treated and prevented by thepresent invention is citrus canker.

BACKGROUND OF THE INVENTION

As reported by the University of Florida Plant Pathology Department,fungal and bacterial pathogens can lower yields, reduce quality,negatively affect the aesthetic and economic value and even ultimatelydestroy plants, crops, pre-harvest fruits, trees, vegetables andgrasses. In particular, bacterial and fungal diseases in citrus plantscreate huge economic burdens on the citrus industry worldwide. Citruscanker alone causes severe economic consequences in the world's citrusgrowing regions. The bacteria which causes citrus canker, Xanthomonascampestris pv. citri, has been found in southern Asia, Japan, the MiddleEast, Africa, South America and now North America. Historically, citruscanker outbreaks have occurred in North America in the early 1900s andagain in 1986. Fortunately, through the use of aggressive eradicationtechniques, the disease was eliminated in both instances. Citrus canker,however, can be reintroduced when people inadvertantly transportinfected citrus fruits and seedlings into citrus growing areas in theU.S. and elsewhere. In the U.S., Florida is by far the state most atrisk from citrus canker given its combination of high humiditythroughout the year, seasonal hurricanes and frequent thunderstormsaccompanied by high wind gusts. (See The University of Florida PlantPathology Department Report atwww.biotech.ufl.edu/PlantContainment/canker.htm)

The University of Florida Extension Service reports that in 1995 citruscanker was again detected in the U.S. in citrus trees in the Miami-DadeCounty, Fla. area. Citrus canker then spread to the commercial groves insouthwest Florida. Since 1998 more than 870,000 trees have beendestroyed in conjunction with eradication programs. (Seehttp://edis.ifas.ufl.edu/FE286)

Costs in managing the threat of citrus canker include capital investmentfor spray equipment, the lost value of affected fruit, costs associatedwith inspection and eradication, and costs associated with the creationof natural windbreaks and other defensive tactics. Current sprayingprograms include relatively expensive copper based sprays. TheUniversity of Florida Extension Service has estimated that if citruscanker became endemic in Florida, the total cost for countering endemiccitrus canker, including the use of copper based sprays, could be morethan $300 per acre.

Many types of organic molecules possess antimicrobial properties and canbe used to effectively control fungal and bacterial disease in plants.However, many of the currently used pesticides are toxic to humans,animals and the exposed environment which limits large scale applicationin, for example, citrus orchards. The Environmental Protection Act wasestablished in 1972, in part, to address concerns over the use ofpotentially toxic materials to control or treat diseases in crops. In1996 Congress passed the Food Quality Protection Act requiring theEnvironmental Protection Agency to reassess the safety and efficacy ofevery existing pesticide by 2006. Concerns about pesticide residues onplants and the exposure of field workers to such residues severelylimits the amounts of pesticide that can be applied and the timing ofsuch application. These limitations decrease the potential effectivenessof commonly used pesticides to prevent and treat bacterial and fungaldisease in plants in general and citrus canker in particular.

Accordingly, there exists a tremendous need for effective, economicaland non-toxic compositions and methods for preventing and treatingbacterial and fungal disease in plants. In particular there is atremendous need for effective, economical and non-toxic compositions andmethods for preventing and treating citrus canker.

SUMMARY OF THE INVENTION

The present invention relates to compositions and methods which preventand treat bacterial and fungal disease in plants. More particularly, thepresent invention is effective in preventing and treating citrus cankercaused by the bacteria Xanthomonas campestris pv. citri. Thecompositions of the present invention include combinations of wax,d-limonene and monohydric alcohol. Applicants have unexpectedly foundthat combinations of these and similar ingredients provide compositionsthat are capable of preventing and treating bacterial and fungal diseasein plants, including citrus canker.

Moreover, compositions according to the present invention do not includetoxic chemicals or chemicals at toxic levels. Accordingly, there areminimal regulatory limitations for the use of such compositions.

The present invention also provides methods of making and using suchcompositions. In one embodiment, a method of this invention includes thesteps of (1) heating water; (2) adding monohydric alcohol to the waterand mixing; (3) adding d-limonene to the mixture and mixing further; (4)adding wax to the mixture and mixing further; (5) optionally filteringthe mixture; and (6) optionally cooling the mixture.

Accordingly, one object of the present invention is to providecompositions for preventing and treating bacterial and fungal disease incitrus trees, especially citrus canker, comprising various combinationsof wax, d-limonene, and monohydric alcohol.

Another object of the present invention is to provide methods of makingcompositions for preventing and treating bacterial and fungal disease incitrus trees, especially citrus canker.

A further object of the present invention is to provide methods ofpreventing and treating disease in citrus trees, including citruscanker, which include applying particular compositions to citrus trees.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides non-toxic, naturally-derived compositionswhich treat and prevent bacterial and fungal diseases in citrus trees,especially citrus canker caused by the bacteria Xanthomonas campestrispv. citri.

The compositions of the present invention may comprise wax, d-limoneneand monohydric alcohol. Applicants have unexpectedly found thatcombinations of these and similar ingredients provide compositions whichare capable of treating and preventing bacterial and fungal disease inplants, especially citrus canker.

As used herein, unless otherwise stated, percentage amounts of aningredient are by total weight of the composition in which thatingredient is included. Compositions of the present invention mayinclude wax material. The preferred wax material is beeswax. Beeswax maycomprise from about 0.005 to about 10.0%, preferably from about 0. 1 toabout 5.0%, and more preferably from about 1.0 to about 2.0% and evenmore preferably about 1.5% of the composition. Optionally, as asubstitute for, or in addition to beeswax, the compositions of thepresent invention may include benzoic acid, salicylic acid and paraffin,alone or in various combinations, in amounts by weight totaling thosegiven above for beeswax alone. Beeswax, benzoic acid, salicylic acid andparaffin are commercially available from many sources.

Compositions of the present invention may also include d-limonene.D-limonene is the major component of the oil extracted from citrus rind.D-limonene has been used extensively as an ingredient in cleaningproducts. D-limonene in compositions according to the present inventionmay comprise from about 0.5% to about 20.0%, preferably from about 5.0%to about 15.0%, and more preferably from about 9.0% to about 11.0%.D-limonene is commercially available from many sources.

Compositions of the present invention may also include monohydricalcohols such as methanol, ethanol and butanol, alone or in variouscombinations. A preferred monohydric alcohol is ethanol. A preferredcombination of monohydric alcohols includes ethanol and methanol.Monohydric alcohols according to the present invention may be eitherdenatured or non-denatured. The monohydric alcohol may comprise fromabout 0.5% to about 15.0%, more preferably about 2.0 to about 12.0%, andeven more preferably from about 4.0 to about 9.0% of the composition.Monohydric alcohols are commercially available from many sources.

Compositions of the present invention also may include other excipients.Other excipients may include potassium hydroxide, xanthan gum, andhydrochloric acid. Potassium hydroxide and hydrochloric acid may be usedto control and adjust pH levels. Xanthan gum may be used to control andadjust viscosity and also provide product stability. When included incompositions according to the present invention, potassium hydroxide maycomprise from about 0.01 to about 5.0%, more preferably from about 0.05%to about 2.0%, and even more preferably from about 0. 1 to about 0.5% ofthe composition. When included in compositions according to the presentinvention, xanthan gum may comprise from about 0.01 to about 2.0%,preferably from about 0.01 to about 1.0%, and more preferably from about0.1 to about 0.5% of the composition.

The balance of the composition may comprise water. The water may bepurified and, if so, preferably has a bacterial colony count of lessthan about 100 colonies per ml. The amount of water used may be variedbased on the desired concentration of the composition. The water may bemade alkaline by the addition of potassium hydroxide and preferably hasa pH above about 10.0. The preferred water hardness is less than 1 grainper gallon or less than 50 ppm.

Methods of Making

The present invention also provides methods of making the compositionsdescribed herein. Such methods may include the steps of (1) addingmonohydric alcohol to water and mixing; (2) heating the alcohol andwater mixture; (3) adding d-limonene and mixing; (4) heating themonohydric alcohol, d-limonene and water combination; (5) adding wax andmixing further; (6) heating the monohydric alcohol, d-limonene, wax andwater mixture; (7) optionally filtering the mixture; and (8) optionallycooling the filtrate.

In another embodiment the method of making compositions includes thesteps of (1) adding potassium hydroxide to water and mixing; (2) addingmonohydric alcohol (e.g., ethanol) to the water and mixing; (3) heatingthe potassium hydroxide, alcohol, and water mixture to about 175° F. forfive minutes or less; (4) adding d-limonene to the water and mixing,while maintaining the temperature at about 175° F. for about 15 minutes(4) adding beeswax to the water and mixing, while maintaining thetemperature at about 170° F. for about 15 minutes; (5) adding xanthangum and mixing vigorously while allowing the mixture to cool; (6)filtering the cooled mixture.

It should be noted that the order of steps recited above in embodimentsof the present invention may be varied to produce compositions accordingto the present invention. For example, d-limonene may be added prior toadding monohydric alcohol or wax could be added before either d-limoneneor monohydric alcohol.

In certain examples of embodiments of the present invention, the watermay be heated in any heating step (if the particular method of makingthe composition includes such) to between about 110° to about 272° F.,preferably to between about 130° to about 210° F., and more preferablyto between about 165° to about 180 F.

The liquid mixture may then be pumped through filters at a pressuresufficient to effectively collect the composition. The filteringpressure may be from about 5 to about 100 psi, preferably is from about10 to about 40 psi, and more preferably is about 30 psi. The compositionmay be cooled before use. Preferably the composition may be cooled to atleast about 95° F. Cooling may be facilitated by the use of a heatexchanger.

Compositions according to the present invention may also be formed intoa crystalline powder form to facilitate packaging, storage and use. Thismay be achieved, for example, by reducing the water content to about 10%of the composition, adding xanthan gum and gum arabic in roughly equalamounts, drying the composition, and then grinding to break up largerparticles. Drying may be achieved by, for example, a vacuum drier, afluidized bed drier, a low temperature roller drier, a vacuum extrusiondrier or by other drying means.

Methods of Using

The present invention also includes methods of using compositions whichcan prevent and treat bacterial and fungal diseases in plants, espciallycitrus canker. An effective amount of the compositions of the presentinvention can be applied to, for example, citrus trees. In this contextan effective amount means an amount that is sufficient to prevent andreduce bacterial or fungal disease affecting citrus trees. Accordingly,an effective amount can vary depending on whether the primary purposeprevention or treatment, and if the latter, the severity of the diseasestate. In general, however, the compositions of the present inventionmay be effectively applied to citrus trees in a concentration rangingfrom about 1% to about 80%. Preferably, the concentration will bebetween 10% and 50% and more preferably between 20% and 40%.

Compositions according to the present invention can be sprayed ontotrees without any observable disease using conventional spray equipment.Likewise, these compositions can be sprayed onto diseased trees in thesame manner. For use in diseased trees, the concentration ofcompositions according to the present invention generally will be higherthan for preventative treatments.

Compositions of the present invention may reduce or eliminate the growthof a wide range of disease-causing organisms in plants, including citrustrees. These compositions have been shown to be especially effective inthe treatment and prevention of citrus canker caused by Xanthomonascampestris pv. citri.

EXAMPLE

The composition as shown in Table 1 was used to demonstrate theeffectiveness of an exemplary embodiment of the present invention intreating citrus canker: TABLE 1 monohydric alcohol (ethanol) 6.65%d-limonene 10.00% beeswax 1.47% water 81.40 potassium hydroxide 0.16%xanthan gum 0.16%Ten citrus trees with existing canker lesions were drench sprayed with a25% solution of the composition according to Table 1, while ten citrustrees were used as controls. Tree limbs were tagged with strips ofcaution tape to facilitate precise identification of the treatmenttrees. Weekly observations were taken to determine the effect of thetreatment on the canker lesions. A second treatment was appliedapproximately two weeks after the first. Over the course of eight weeksof observation, canker lesions had not expanded on the ten treatmenttrees, while canker lesions had grown substantially on the ten controltrees. The treatment trees and control trees both exhibited similarinsubstantial levels of leaf wilting and fruit drop.

1-21. (canceled)
 22. A method for reducing the incidence of disease in aplant species comprising applying to said plant species a compositionwhich comprises monohydric alcohol, d-limonene, and wax or wax extract.23. The method of claim 22, wherein the plant species is citrus.
 24. Themethod of claim 23, wherein the disease is citrus canker.
 25. The methodof claim 22, wherein the wax comprises beeswax or extract of beeswax.26. The method of claim 22, wherein the monohydric alcohol is selectedfrom the group consisting of ethanol, methanol and butanol, alone or incombination.
 27. The method of claim 26, wherein the wax comprisesbeeswax or extract of beeswax.
 28. The method of claim 27, wherein theplant is a member of a citrus species and the disease is citrus canker.29. The method of claim 28, wherein the composition is applied byspraying.